can i configure my reliance broadnet as router

basically i have 2 computers in my house
i want to share the internet connection

i do not want to share the connectionwith windows xp connection sharing wizard

what i want 2 say is that suppose my 1 comp is off
i can still connect through the other


is airtel providing 256kbps connection unlimited in kolkata ?
whats the charges
at night speed doubled?